Lay the fries in a single layer on a baking sheet and cook as directed on the package, until frim and crisp. Remove from oven and sprinkle with seasoned salt, toss to coat
While the fries are baking, cook the ground beef and onion in a skillet. Cook over medium heat until onion is soft and no pink remains on the beef. Drain any excess fat. Add in the taco seasoning and salsa, mix to combine and heat through
Sprinkle half the shredded cheese over the fries, then spoon on the meat mixture as evenly as you can. Top with the remaining shredded cheese. Place the nacho fries back into the oven to melt the cheese, if necessary.